Railway-traffic-controlling apparatus



Jan. 1,1929. 1,697,680

A. V. T. DAY

RAILWAY TRAFFIC CONTROLLING APPARATUS ori inal Filed June 4, 1915 Brake Pg'ue fi'onz [er INVENTOR Patented Jan. 1, 1929.

iii iirsn ALBERT V. T. DAY, O PARIS, FRANCE, ASSIGNOR- T0 THE "UNEGN SWITCH & SIGNAL v iswsso COMPANY, OF SVJISSVALE, PENNSYLVANIA, A CORPORATION OI? ?E1\TI\TSYLVANIA.

RAIL'WAY-TEAFFI -CONTROLLIIJG APPARATUS.

Original application filed June 4, 1913, Serial No. 771,650. Renewed March 14, 1922, Serial No.- 543,767, now Patent No. 1,479,286, dated January 1, 1924. Divided and. this application filed October 19, 1923.

Serial No. 669,501.

My invention relates to railway trailic controlling apparatus, and particularly to apparatus carried on a railway train tor automatically controlling the brakes.

The present application is a division of my copending application filed on the 14th day of March, 1922, Serial No. 54$,(67, now Patent No. 1,479,286, dated January 1, 1924, for railway train control systems, wh ch applicationis a renewal of my application filed on the 4th day of June, 1913, Serial No. 771,650 for the same invention.

1 will describe one form of apparatus c nbodyino my invention, and will then point out the novel features thereof in claims.

The accompanying drawing is a v ew showing one form of apparatus embody ng my invention.

Referring to the drawing, the apparatus in the form here shown comprises a stop solenoid 196 which is normally energized, but becomes de-ener -ized when a condition arises which necessitates an auto1natic application of the brakes. As here shown, this solenoid is normally energized through a circuit local to the railway vehicle and w ".ch may be traced follows: from the vehicle battery 52 through the contacts 53 normally closed by the relay 54, and thence through the wire 55, solenoid 196 and wire back to the battery. The relay 54 is normally energized by a current flowing from the battery 52 through the contacts 57 also normally closed by the relay 54, and thence through the wire 58, contact plate 59, contact spring 60, wire 61, relay 54 and wires 62 and 56 back to the battery. The contact spring 60 is mounted on the upper end of the stem 63 which slides in the insulated bearing and carries the contact shoe 65 adapted to engage short rainp rails such as located at successive points along the railway. It will be noted that, if the local circuit of the relay 54 is once de-cnerized so as to open its contacts 53 and 57, inc local battery 52 will be open-circuitod and the relay 54 cannot be re-energized by this battery until it has first been re-energized by extraneous current in order to reclose the contacts which it controls. long as the relay is de-energized, the soleits circuit is controlled by the contacts 53 governed by the relay 54. i

The signal 67 is a distant or caution signal, which in any well known manner will be cleared when the track is clear from the insulated rail joints 68 up to a point some distance in advance of 69. This signal governs the circuit controller 70 so that the same will be closed when the signal is clear and will be open when the signal is in its caution position.

Let it be assumed that the contact shoe 65 engages the ramp rail 66 when the advance end 01" the train or vehiclereaches the insulated joints 6S n1arking the rearinost end of the track section'whioh governs the signal 67. Now, if thisisignal is in clear position when the local circuit of the relay 54 is broken at the contacts-59, by the rise of the spring 60 as the shoe rides up on the ramp rail 66, the relay 54 will not be ole-energized by this breaking of its local circuit since this circuit willbe replaced by a circuit including the external battery 71.

which latter circuit comes into action be-- fore the local circuit is broken and which may be traced asfollows: from the battery 71 through the semaphore-controlled circuit breaker and thence through the wire 72, ramp rail 66, .contact shoe 65, shoe stem 63, wire 61, the relay 54 and wires 62,56 and 73 to the axle of the vehicle wheel 24, and thence through the track rail to the wire 74 and back. to the battery. As the shoe leaves the ramp rail, the contacts 59, 60 in the local circuit are reestablished before the contact between the shoe and ramp rail is discontinued, whereby the local battery 52 is re-connected with the relay 54 before the extraneous battery 71 is disconnected therefrom. Hence the act of running over the ramp rail 66. produces no eli'ect upon the relay 54 when the signal 67 is clear, and hence the solenoid 196 is not affected in passing a clear signal. But if the signal 67 is in its caution position when the shoe 65 rides over the ramp 66, the breaking of the contacts 59, 60in the local circuit of the relay 54, will de-energize this relay and open its contacts-53 to de-energize the solenoid 196; and this relay and the acid 196 will also be tie-energized because Solenold Cannot be l the brake pipe.

' gineers valve to the brake pipe, although air may be taken from the brake pipe through the engineers valve by way of the check valve 185 which constitutes areturn by-pass around the port 182. Hence, when the port 182 is closed, it will be impossible to charge the brake pipe or release the brakes, although the engineers valve will still be available to make a service or emer- V gency application.

The relay valve 186 consists in a vertically disposed cylindrical valve chamber, the upper end of which communicates with the main reservoir 17 8 and the lower end of which communicates with the atmosphere, but is normally closed by the valve piston 187 mounted on a' common stem with an upper valve piston 188 normally disposed in the upper enlarged chamber of the valve casing with ample clearance for the flow of air past the piston and through the middle smaller chamber 186 to the pipe 189. The valve stem is secured in the upper end of a core 195 normally held by the solenoid 196 which normally sustains the valve against the pressure of air tending to force the pistons downward. Normally the main reser voir communicates freely through the relay valve casing with the pipes 189 and 190 leading to the lower end of the throttling cylinder 191, and also leading through the adjustable pin valve 192 and check valve 197 in parallel with each other, and thence to the timing-reservoir 193 and to the lower end of the middle chamber 194 of the monitor main valve. The upper valve-piston 188 fits the restricted middle bore 186* of the valve cas ing so that, when the solenoid 196 is deenergized and drops its core, the piston 188 will close the bore 186, thus shutting ofl communication between the main reservoir and the pipe 189, while this pipe will be opened to the atmosphere through the bottom bore of the valve casing from which the lower piston 187 emerges after the upper piston 188 has closed the bore 186.

The casing of the monitor main valve 183 comprises three cylindrical bores, the upper, middle and lower, of difierent diameters, the middle being the largest, the upper next in order, and the lower bore being the smallest.

under side to receive the upper end of the balancing spring 198 which surrounds the lower smallest piston and rests on the bottom of the middle chamber of the valve casing. The balancing spring is a light spring normally expanded to its full length with a considerable clearance bet-ween its upper end and the top of the annular recess, so that the piston valve which normally occupies its uppermost position, will travel some distance downward before it engages the spring. The upper piston of the valve is axially bored from its upper end, and the port 182 consists in a radial hole passing through the wall of the piston, communicating with its axial bore, and normally registering with a port in the valve casing which communicates with the pipe 181. A vent port 199 leads from the atmosphere into the middle chamber of the valve casing near the upper end of the chamber. A port 200 leads end of this lower chamber is connected with the balancing reservoir 201.

The throttling cylinder 191 comprises upper and lower cylindrical chambers of different diameters, the lower being the larger, and the piston valve within the cylinder comprises a long and short section fitting these bores respectively. Steam from the locomotive boiler enters the upper end oi the throttling cylinder and passes through an axial bore in the upper section of the piston valve and thence through'the lateral port, a connecting pipe, and the manually controlled throttle to the locomotive cylin ders. The area of the lower end of the piston valve will exceed the area of the upper end sufficiently to insure a total air pressure on the lower end exceeding the total steam pressure on the upper end sufliciently to hold the piston valve in its uppermost position holding its steam port open as indicated. When the air pressure underneath the piston is released or sufliciently diminished, the piston will be forced downward by the steam pressure so as to close the steam port leading from the locomotive boiler to the hand throttle 202.

The timing-reservoir 193 and the middle chamber 194 of the monitor main-valve casing are normally filled with air at main reservoir pressure, and the balancing reservoir 201 and the bottom chamber 200 of the monitor main-valve casing are normally filled with air at brake pipe pressure. When the. stop solenoid 196 is de-energized,'to drop its core 195 and the valve-pistons 187 and 188 reevgeso connected thereivith,the main reservoir is cut off from the timing reservoir and the valve chamber 194, and the timing reservoir and this valve chamber are opened to the atmosphere, as before explained, by way or" the adjustable pin-valve 192, the pipe 189 and the lower end of the relay valve casing which is now open. Since the air from the timing reservoir and valve chamber 194 cannot flow backward through the check valve 197, the pin-valve controls the efllux of air from this reservoir and valve chamber and determines the rate at which the air pressure therein will be gradually diminished.

The upper end of the piston-valve is alpipe pressure, but since the p, -.te oi the are the middle piston and the lower piston exceed the area of the upper piston, and since the air pressure on the lower piston normally equals that on the upper piston, while the air pressure on the middle piston normally exceeds that on the upper piston, it "follows that the total upward pressure on the middle and lower pistons must normally exceed the pressure on the upper piston in a degree sutlicient to hold the piston valve firn'i y in its uppermost normal posit-ion as i icated. Howom the timing;

ewr, as the air is vent-ed reservoir 193 and the middle c amber 194 in iii) of the valve casing, the pressure therein gradually reduced until. the total upward pressure on the valve piston just equals the downward air pressure thereon plus the gravity of the valve. To vent the pressure of the middle chamber 194 down to this point may occupy several seconds after the stop solenoid 196 is (lo-energized, but this lapse oi time will, in any event, be inimaterial in the saliegguarding function the apparatus. At this instant, the piston-valve moves downward, shutting oil communication between the piston-port 182 and thepipe 181, and closing t re port 200 to shut off communication between the brake pipe and the balancing reservoir 201. The lower side of the port 182 reaches the shoulder between the upper and middle chambers of the valve casing, just as the middle piston of the valve engages the light balancing spring 198.

Now, it must be noted that at this instant no air has been vented from the brake pipe, wherefore the pressure on the upper end of the piston-valve equal. to the full brake pipe pressure trapped in the balancing reservoir 201 and exerted on the bottom piston oi? the valve having an area considerably smaller than its upper piston; and the difference in total forces exerted by these equal air pressures on the difi'erent areas of the upper and lower valve ends, is balanced by the reduced'air pressure on the lower side of the iiddle piston. Hence, from this instant on, the etllur. off air from the timing reservoir and middle valve chamber must be accompanied by an efilux of air through the port 182, upper end oi the middle chamber and port 199, to the atmosphere, at a rate which will maintain a balanced condition and. position or" the piston valve. That is to say, as the air spills out of the timingreservoir and middle valve chamber 194, the consequent reduction of pressure therein tends to lower the piston valve slightly against the light opposition of the balancing spring 198, thus moving the lower side of the port 182 more or less below the registering shoulder so as to spill the air from the brake pipe to the atmosphere sufiiciently to reduce the. total brake pipe pressure on the upper end of the piston valve in substantially exact proportion to the reduction of pressure exerted on the middle piston. To better explain this, it may be stated that ii the piston valve were placed in a position leaving the port 182 wide open to the port 199, the air would spill from the brake pipe much faster than would be necessary to balance the diminution of pressurein the middle valve chamber, where upon the pressure in the middle chamber would immediately preponderate and raise the piston valve to restrict the area of the vent port to the aforesaid balancing point or point or" proportionate eiilux. ()n the other hand, in it be assumed that thepiston valve be raiseo slightly above this balancing position, it must be noted. that the rate eillux from the brake pipe will be insuliicient to compensate the e'fllux from the timing reservoir and middle chamber 194, whereupon a more rapid fall of pressure'in the middle chamber will cause the brake pipe pressure to preponderate and lower the piston valve to the aforesaid balancing point.

Also it must be noted that the valve will automatically reduce the pressure in the brake pipe at the definite constant rate de termined by the fall of pressure in the tin"- ing reservoir and middle valve chamber, regardless of the length of train and brake pipe involved. It the locomotive be running without a train or with but one or two cars, a very small openin of the vent port 182 at the shoulder opposite the port 199wi.ll sufflee to reduce the pressure in this short brake pipe (necessarily of small. capacity) at the definite rate of pressure reduction occurring in the middle chamber 194, and the valve will automatically restrict the area of the vent port 182 to maintain this definite rate of reduction in the brake pipe. On the other hand, if the locomotive be pulling a very long train of freight cars with a consequently long brake pipe of great capacity, it will require amuch larger opening of the vent port 182 to reduce the pressure in this greater brake pipe at the same fixed rate proportionate to the fall of pressure in the middle chamber 194, but the alve will auto-.

matically adjust itself to accomplish this same rate of reduction in the long brake pipe, inasmuch as any insufficiency of area at the vent port 182 would immediately result in a preponderance of pressure on the upper end of the piston valve, tending at once to increase the area of the vent port to the aforesaid balancing point.

Also, if the engine driver should make a manual service reduction through the brake valve 179 by way of the check valve 185, concurrently with an automatic service ap plication through the vent ports 182, 199 of the monitor valve, this valve would still operate to maintain the aforesaid definite rate of pressure reduction in the brake pipe as determined by the fall of pressure in the middle valve chamber 1% and regardless of the manual service application, since any reduction of brake pipe pressure in excess of this definite rate, whether resulting from the automatic service vent or the manual 7 service vent, or from both together, would immediately cause a preponderance of pressure in the middle chamber 194 tending to raise the piston valve and restrict the automatic vent 182 to a point effecting the said proportionate rate of reduction. That is to say, when a manual service application conours with the automatic service application, the monitor valve automatically diminishes the rate of flow through the automatic vent by an amount exactly equal to the supplement flow through the manually controlled service vent; and this automatic restriction of the automatic vent will continue as'tlie manual vent is increased until the manual vent alone discharges the brake pipe at a rate equal to the aforesaid definite rate of pressure reduction determined by the fall of pressure in the middle chamber 194, after which the automatic vent will remain entirely closed, and. after which the rate of pressure reduction in the brake pipe will be increased if the area of the manual venting is further increased. 7

But in the practice of my invention, however, the aforesaid definite rate of automatic pressure reduction in the brake pipe as determined by the fall of pressure in the timing reservoir 193 and middle chamber of the monitor valve will be nearly the quickest possible service reduction, that is, nearly the greatest rate of venting possible without incurring the emergency application of the brakes. This is necessary in order to operate in the smallest braking distance compatible with safety, so that the engine driver may have the greatest latitude in the control of his train and the exercise of his judgment to meet the varied and complex requirements of commercial schedules. But it would be prohibitory to thus automatically open a maximum rate service vent with the possibility of a concurrent manual service application, if the effects of the two vents were to be cumulative in-their discharge of air from the brake pipe, since any substantial manual vent added to an automatic vent of maximum or nearly maximum service rate would incur an unexpected and unwarranted emergency application of the brakes which would be disastrous in many situations, and objectionable always. An automatic ap pl cation of the brakes at, or nearly at, the maximum service rate is not objectionable, however, in an automatic train control system such as the one here under consideration, in which such an automatic service application is an abnormal incident occurring only as a result of the engine drivers negligence after due warning of the necessity a manual application of the brakes.

Wot only is the foregoing balancing function of the monitor main valve necessary to apply the brakes at the maximum service rate without danger of incurring an emergency application through. concurrent service manipulation of the engineers valve, but it is also necessary to obtain the'maximum service rate of reduction without liability of incurring an emergency application by a variation in the length of brake pipe. For instance, it will be apparent that it the automatic valve were set to open a definite invariable vent port which would discharge a long brake pipe at the maximum service rate, the same fixed vent would reduce the pressure in a short brake pipe at a greater rate which would inevitably incur the emergency application of the brakes.

Those versed in the air brake art are familiar with the new system of air brakes recently developed by the Westinghouse Air Brake Company to accomplish a substan tially uniform pressure reduction and uniform brake application in exceedingly long freight trains, and which accomplishes this result by automatically opening a supplemental ventfrom the brake pipe at each triple valve throughout the train, in response to an initial. service reduction at the engineers valve. Obviously, to effect a full service reduction at the maximum service rate in a brake pipe of given length equipped with such triple valves, will require a smaller service vent at the locomotive end of the brake pipe, than would be required to accomplish. an. equivalent reduction in a brake pipe of the same length equipped with the older style triple valves not operating to open individual supplemental vents; but it will be understood that the balancing action of the monitor main valve automatically adapts the automatic service vent to effect the required full service reduction at maximum service rate in a brake pipe equipped with the new style triples, by automatically restraining the vent controlled by the balancing valve so as to compensate for the supplemental vents opened at successive points throughout the brake pipe, practically in the same manner as the before explained compensation fora manual service vent concurrent with the automaticapplication. of the brakes.

It will now be apparent that the balancing monitor valve automatically governs the automatic service vent to effect the maximum service rate of braking regardless of all extraneous incidents and conditions of service.

Although at the present writing I deem most expedient to apply the bakes at "no maximum service rate-when the soleplained balancing position and the proportionate :ato'of bralrc pipe discharge resulting from its balancing action. After the are in the timing chamber 194 has ach-ed the atmospheric value, any further sh ischarge of air from the brake pipe t the ports 182, 199 would immedir "ed ce the pressure on the upper end the monitor valve in a slight degree sufdc ent to cause a preponderance of upward tirust from the light balancing spring 198 and the air trapped in the balancing reser- 291 and lower chamber of the valve at initial or normal brake pipe pressure. preponderance of upward thrust raises the piston valve just far enough to close its automatic vent port, and since the pressure exerted by thebalancing spring will always be very light, it follows that while the piston valve is thus balanced with its vent port 182 just above the shoulder leading to the port 199, the pressure in the upper chamber of the valve casing, which is the terminal brake pipe pressure, must'bea'r a definite rati to the initial brake pipe pres sure trapped in the balancing reservoir, which ratio must be the inverse of the ratio of areas of the opposite ends of the valve.-

This

tial pressure may be. The constant perccntage of pressure reduction thus effected, will be that which is necessary for a full or maximum service application the brakes, so that the balancing monitor valve will always effect the full service application of the brakes without waste of brake pipe air beyond the pressure reduction necessary to efi'ect' this result. a

The escape of air from the timing reservoir 193 ad timing chamber 19% will, of course, be less rapid as the pressure therein approaches atmospheric value, so that the rate of pr uire reduction therein will be relatively slow during the last moments of the efiiux; and, since the balancing action of the valve makes the rate of reduction in the brake pipe always substantially proportionate to the reduction rate in the. timing reservoir and timing chamber, it is apparent tint the rate of pressure reduction in the brake pipe will decrease toward the end or the discharge, or, in other words, will be tapered oil gradually as the Vi-Elli; through the ports 182, 199 is gr dually closed T his gradual cutting off of the automatic service vent prevents the kick-off of the brakes at the front end of the train which is frequently incurred by a too-sudden closing of a. large service vent, owing to a rise inthe pressure at the head end ofthe brake pipe due to the momentum of its air flowing'i orward toward the vent.

lt has already been noted that a manual service applicationo'f the brakes at the engineers valve 179, concurrently with the automatic service application, will not affect the definite rate of service application brake pipe through the check valve 185 and emergency port of the engineers valve 179,

and the automatic closing of the vent port 182 by the balancing action of the monitor valve only serves tdcompensate the flow of air through the engineers valve up to the :Eullv service rate, after which any greater rate of discharge at the engineers valve will be cumulative and fully effective on the brake pipe pressure.

When the stop solenoid 196 is re-enen gized, it restores the valve pistons 187 and 188 to their normal positions as indicated, thus re-establishing communication between the main reservoir and the pipe 189 and permitting a rapid flow otmain reservoir air through the check valve 197 into the timing reservoir 193 and middle chamber of timing chamber 194 of the monitor main valve, thus quickly restoring the valve to .lll)

its normal position as shown, andreplacing the port 182 in register with the pipe 181 to permit the flow of brake-releasing and charging air from the engineers valve 179 through the pipe 181, port 182, and pipe 184 to the brake pipe.

It will now be apparent, that each time the brakes are automatically applied by de-energization of the stop solenoid 196, the venting of the pipe 189 to the atmosphere releases the pressure in the lower end of the throttling cylinder 191, so as to cut off com munication from the steam boiler to the manually controlled throttle 202, and thus discontinue the application of power in the locomotive cylinders. Each time that the stop solenoid is re-energized, the throttling cylinder is re-connected with the main reservoir which thereupon re-charges the throttling cylinder and raises its piston valve to re-establish power communication from the steam boiler to the locomotive cylinders.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims Withoutdeparting from the spirit and scope of my invention.

. Having thus described my invention, what I claim is:

1. Air brake apparatus for railway trains comprising a brake'pipe under pressure, a chamber normally in communication with said brake pipe, means for disconnecting said chamber from the brake pipe and for exhausting said brake pipe to atmosphere to apply the brakes, and means for balancing the initial brake pipe pressure in said chamber against a predetermined lower pressure in said brake pipe to limit the reduction in brake pipe pressure to said predetermined lower pressure.

2. Air brake apparatus for railway trains comprising a brake pipe under pressure, a chamber normally in communication with said brake pipe, means for disconnecting said chamber from the brake pipe and for exhaustingsaid brake pipe to atmosphere to apply the brakes, a diflerential valve having a larger piston exposed to brake pipe pressure and a smaller opposing piston exposed to the initial brake pipe pressure in said chamber; and means controlled by said valve when the force exerted against thesmaller piston exceeds that exerted against the larger for cutting off the exhaust from said brake pipe.

3. Air brake apparatus for railway trains comprising a brake pipe under pressure, a

chamber normally in communication with said brake pipe, means for disconnecting said chamber from the brake plpe and for exhaustingsard brake pipe to atmosphere to comprising a brake pipe under pressure, a

chamber normally in communication with said brake pipe, means for disconnecting said chamber from the brake pipe and for exhausting said brake pipe to atmosphere to apply the brakes, a differential valve having a surface exposed to brake pipe pressure and an opposing surface exposed to the initial brake pipe pressure in said chamber, and

means controlled by said valve for cuttingoff the exhaust from said brake pipe actuated by a predetermined excess in the unit pressure on said opposing surface over the unit pressure on said first mentioned surface.

5. Air brake apparatus for railway trains comprising a brake pipe under pressure, a

chamber normally in communication with.

said brake pipe, means for disconnecting said chamber from the brake pipe and for exhausting said brake pipe to atmosphere to apply the brakes, a magnet actuated valve for controlling said means, means for measuring a predetermined diiference in pressure between said chamber and the brake pipe, and means actuated by the pressure in said chamber for cutting off the exhaust from the brake pipewhen said predetermined difference in pressure between said chamber and the brake pipe is obtained.

6. In a pneumatic control system for a service brake valve, the combination of an automatic valve limiting the reduction of air pressure in the control system, an actuator for the automatic valve worked by opposing air pressures, and by a pressure inclependent of the air pressures, and means for reducing one of said air pressures without similar reduction of the other pressure.

7. Automatic train control apparatus ineluding a train line pipe connected with a source of fluid pressure and having anengineers valve connected therewith, a by pass pipe between the train line and the engineers valve, and a control valve adapted to be associated with said train line pipe operable automatically by the .speed of the train exceeding a predetermined rate to vent said train line pipe and simultaneously cut oil communication between the latter and the engineers valvo'except through said bypass pipe.

8. An automatic train control apparatus including a train line pipe having a source of fluid pressure supply, a valve adapted to be associated with said pipe for auto matically venting and cutting the sameoff from its source of fluid pressure supply when the speed of the train exceeds a predetermined rate, said valve including a casing having a bore therein opening at one end through one side thereof, the train line being in communication with said bore, and a member slidable in said bore and operable when at the limit of its sliding movement in one direction to close the open end of said bore and permit communication between the train line and its supply, and operable when at the limit of its sliding movement in the other direction to cut elf communication between the train line and its supply, and simultaneously open the lower end of said bore whereby the train line is vented, and means for operating said member.

9. In automatic train control apparatus, the combination with the train pipe and the pressure supply pipe of an air brake system; of a speed control valve arranged between said pipes and operable automatically by the speed of the train exceeding a predetermined rate to vent the train pipe and cut oil the supply thereto, and a bypass pipe connecting the train pipe with the pressure supply pipe, said by-pass pipe having a check valve therein opening in the direction of the supply pipe whereby air may be drawn at all times from the train pipe and whereby air may be supplied to the train pipe only through said speed control valve.

10. In automatic train control apparatus, speed control means including a valve casing provided with ports and having a bore therein opening axially at one end through one side of the casing, a valve in said casing normally permitting communication through said bore between said ports and normally closing the open end of said bore, the train pipe oi the usual air brake system of the train being connected through an aforementioned port with said bore, and means operated by the speed of the train exceeding apredetermined rate to move said valve to close said bore against communication between said ports and to open the normally closed end of said bore.

11. In automatic train control apparatus, speed control means including a valve casing adapted to be connected with the train pipe of the train air brake system and having a bore therein opening axially at one end through one side of the casing, said bore being stepped to provide portions of different diameters thereby to provide a shoulder constituting a valve seat between adjacent stepped portions, a pair of ports entering said bore to opposite sides of said valve seat, respectively, a valve in said casing for cooperation with said seat to permit and deny communication between said ports, and an extension on said valve carrying a valve element for co-operation with the open end of said bore, said extension being of such length that when communication is per mitted through said bore between said ports, said valve element is in closing relation to the open end of said bore,.and when communication is denied through bore between said POTS, said valve element is open with respect to the open end of said bore. f

12. An apparatus for controlling the reduction of brake pipe pressure in a train air brake system comprising a valve mechanism controlling an exhaust port, a pneumatic device having different effective pressure areas on opposite sides thereof for operating the valve mechanism, means for admitting fluid at brake pipe pressure on the valve side of said device, andmeans for admitting and trappin fluid at brake pipe pressureon the opposite side of said device.

13. An apparatus for controlling the r'e duction of brake pipe pressure in a train air brake system comprising a casing, a valve,

therein for controlling an exhaust port, a pneiuiatic devlce having different effective areas on opposite sides thereof for operating the s id valve, a port in said casing for adi' it "131g fluid at brake pipe pressure to the valve side of said device, and means for adi'nitting and trapping iiuid the same pressure on the opposide side of said device,

14. An apparatus for controlling the reduction of brake pipe pressure in a train air brake pipe pressure in a train air brake system comprising a casing, a valve therein controlling an exhaust port, a chamber in said casing, a pneumatic device between said chamber and valve for operating the said valve to produce a reduction'in brake pipe pressure which is always a predetermined percentage of the ini tial brake pipe pressure, means ior admitting fluid at brake pipe pressure onto the valve side of said device, and means for admitting and trapping fluid at the same pressure in said chamber to be effective on the opposite side of said device.

15. An apparatus for controlling the reductionof brake pipe pressure in a train airbrake system comprising a casing, a valve therein controlling an exhaust port, a chamber in said casing, a capacity tank in communication with said chamber, a pneumatic device between said chamber and valve for operating the said valve to produce a reduction in brake pipe pressure which is always a predetermined percentage of the initial brake pipe pressure, means for admitting fluid at brake pipe pressure onto the valve side of said device, and means for admitting and trapping fluid at the same pressure in said chamber to be effective on the opposite side of said device.

16. An apparatus for controlling the reduction of brake pipe pressure in a train air brake system comprising a casing, a valve therein controlling an exhaust port, a chamber in said casing, apneumatic device between said chamber and valve having different effective pressure areas on opposite sides thereof for operating the said valve to produce a reduction in brake pipe pressure which is always a predetermined percentage of the initial brake pipe pressure, means for admitting fluid at brake pipe pressure onto the valve side of said device, and means for admitting and trapping fluid at the same pressure in said chamber to be eii'ective on the opposite side of said device.

17. In combination, a railway vehicle provided with a braking system, a reservoir normally in communication with said braking system, means for simultaneously trapping air in said reservoir at the initial pressure in said braking systemand permitting reduction of pressure in the braking system, and means controlled ointly by the initial braking system pressure in said reservoir and the actual pressure in the braking system for discontinuing the reduction of pressure in the braking system. v

18. Air brake apparatus for railway trains comprising a brake pipe under pressure, a reservoir, means for trapping air at initial brake pipe pressure in said reservoir and reducing the pressure in said brake pipe to apply the brakes, and a valve controlled in part by the initial brake pipe pressure in said reservoir to limit the reduction in brake pipe pressure.

19. Air brake apparatus for railway trains, comprising a brake pipe under pressure, a chamber normally in communication with said brake pipe, means for simultaneously trapping initial brake pipe pressure in said chamber and venting the brake pipe to atmosphere to apply the brakes, and means controlled in part by the initial brake pipe pressure in said chamber for determining the final brake pipe pressure.

20. In combination, a railway vehicle provided with a braking system, means for automatically reducing the pressure in said braking system to cause a brake application, and means for limiting the automatic reduction of pressure in said braking system comprising a reservoir in which air is trapped att-he initial pressure in the braking system.

21. In combination, a railway vehicle provided with a braking system, a reservoir normally in communication with said braking system, and a valve device for trapping air at initial braking system pressure in said reservoir and permitting a limited reduction of pressure in the braking system determined in part by the initial pressure trapped in said reservoir. 7

22. In combination, a railway vehicle provided with a braking system, a reservoir normally in communication with said braking system, means operating upon initiation of an automatic brake application to disconnect said reservoir from the braking sys-' tem and trap initial braking system pressure in the reservoir, and means controlled by the trapped pressure in said reservoir for limiting the reduction in said system.

23. In combination, a railway Vehicle provided with a braking system, means for automatically reducing the pressure in said braking system to cause an application of the brakes, and means including a reservoir in which the initial pressure in said system is trapped for limiting the reduction of pressure in said system. H

In testimony whereof I afliX my signature.

ALBERT V. T. DAY. 

